After analyzing records on more than 4,000 children with ADHD, the investigators found that nearly 72 percent of them took part in one or more after-school activities. And if they did, they missed fewer days of school and had less severe symptoms of the disorder.

"Anecdotally, we've heard that having a diagnosis of ADHD can sometimes be a deterrent for participating in after-school activity programs," explained study co-author Dr. Nicole Brown. She's a pediatrician at Children's Hospital at Montefiore in New York City.

"So, I was surprised to see that high prevalence of participation" among children with ADHD, Brown added. "I thought it would be lower, and it's encouraging that it's that high."

A syndrome affecting more than 11 million Americans, ADHD is marked by problems with restlessness, paying attention and controlling impulses, according to the Attention Deficit Disorder Association. The condition is typically diagnosed among children in grade school, and medications and/or behavioral therapy are popular treatment options.

Prior research found that children with ADHD are at higher risk for missing school more often, and disruptive school behaviors. The new research set out to determine not only how many kids with ADHD take part in after-school activities, but also the link between doing so and the number of missed school days and calls home from school.

Brown and her colleagues identified 4,185 children aged 5 to 17 with ADHD. Their parents had also reported the severity of their child's condition; the number of school days missed in the prior 12 months due to illness or injury; and the number of calls home from school for a problem in the prior year.

The analysis showed that children with ADHD who participated in after-school activities had nearly 40 percent lower odds of parents reporting them having a moderate or severe case. Additionally, after-school activity participation was also associated with 60 percent lower odds of missing seven or more school days in a year. But the study did not prove a cause-and-effect relationship.

No significant associations were found between taking part in after-school activities and receiving calls home from school.

Study co-author Dr. Yonit Lax, a pediatrician at Maimonides Medical Center in New York City, said her team has several ideas why the results indicated kids with ADHD benefit from after-school activities. Prior research has established that increased physical activity and less screen time among these children are both linked to less severe cases, she said.

"Looking at those two factors, it really reinforces what we're thinking -- that those placed in a more structured environment, outside screen time, have lower odds of moderate or severe ADHD," Lax said.

Dr. Daniel Glasstetter Jr. is a pediatrician at Christiana Care Health System in Wilmington, Del. He said he was encouraged by the finding that more than seven in 10 children with ADHD took part in after-school programs.

"Intuitively, to me, that seems like a high number, which is good," he said. "But not having a comparison to a control group [of children without ADHD], I'm not sure that's higher or lower than what the student population would be doing."

Glasstetter added that more research is needed to determine why after-school programs would lessen the likelihood of moderate or severe cases of ADHD.

Lax said she hoped the research would encourage pediatricians to consider promoting after-school activities to parents as part of a larger strategy to benefit children with ADHD.

"It's part of our clinical toolbox when thinking of treating the whole patient," she said.

Brown said the findings suggest that strategies to treat ADHD shouldn't just consist of medication and behavioral therapy.

"There are a lot of other resources in the community that can potentially lower symptom severity and improve outcome," she said. "This is one potential strategy to think of at a community level."

The study was presented Saturday at the Pediatric Academic Societies annual meeting in Toronto. Research presented at meetings should be viewed as preliminary until published in a peer-reviewed journal.